Report on Arenal (Costa Rica) — 28 March-3 April 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
28 March-3 April 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Arenal (Costa Rica). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 28 March-3 April 2001. Smithsonian Institution and US Geological Survey.
10.463°N, 84.703°W; summit elev. 1670 m
All times are local (unless otherwise noted)
On 29 March OVSICORI-UNA personnel visited the area affected by pyroclastic flows that traveled down the flanks of Arenal on 24, 25, and 26 March. The pyroclastic-flow deposits were located on the N and NE flanks of the volcano. The ash clouds produced from the pyroclastic flows drifted towards the W and SW, depositing ash on an area up to 10 km2 including two towns. Some of the block-and-ash deposits were several meters thick and the debris fan was up to 250 m wide. There were no reports of injuries or damage to buildings.
Geological Summary. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1670-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. Arenal lies along a volcanic chain that has migrated to the NW from the late-Pleistocene Los Perdidos lava domes through the Pleistocene-to-Holocene Chato volcano, which contains a 500-m-wide, lake-filled summit crater. The earliest known eruptions of Arenal took place about 7000 years ago, and it was active concurrently with Cerro Chato until the activity of Chato ended about 3500 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. An eruptive period that began with a major explosive eruption in 1968 ended in December 2010; continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows characterized the eruption from vents at the summit and on the upper western flank.